1. Field of the Invention
The present invention relates to an apparatus and a method for testing whether integrated circuit (IC) device pins securely contact IC socket terminals.
2. Description of the Related Art
A burn-in test of a semiconductor IC device employs an apparatus for inserting the device into and removing the device from a socket of a burn-in tester. The apparatus typically includes insertion and removal tools that are driven by servomotors. A typical burn-in test procedure includes: inserting an IC device to be tested into a socket on a burn-in board; transferring the burn-in board into a burn-in test chamber; and burn-in testing the IC device.
The burn-in test includes a contact test to verify whether the IC device is correctly inserted in the socket. Conventionally, an operator manually checks whether there is a contact problem between the IC device and the socket. When the operator finds a contact problem, he/she reinserts the IC device to the socket using removal and insertion tools. Referring to FIG. 1, a conventional IC device insertion and removal apparatus for a burn-in test is explained. The conventional apparatus is similar to the apparatus of FIG. 1. A rotating tool (A) is a unit that picks up and transfers IC devices. Rotating tool (A) includes a servomotor control box 158, a rotating tool 124, a tool cylinder 144, and a tool head 146. A tool feeding servomotor 138a is in servomotor control box 158, and a rotating plate 137 is between servomotor control box 158 and rotating tool 124. A rotating servomotor 138b, which rotates a lead screw 140, is in rotating tool 124, and tool cylinder 144 is fixed to lead screw 140 of rotating tool 124 by a fixing member 156, so that rotation of lead screw 140 can move tool cylinder 144 up or down. Tool cylinder 144 has a spline shaft 148 to which tool head 146 is attached, and tool head 146 has a vacuum nozzle (not shown) at its end, which picks up an IC device by a vacuum suction force. The apparatus includes a number of rotating tools (A), each of which has a dedicated function. A loading tool 112, a DC test tool 114, an insertion tool 116, a removal tool 118, and an extension tool 120 of the apparatus are all rotating tools (A).
Loading tool 112, which is on a frame 10 of the apparatus, loads an IC device 162 to be tested from an IC tray 160 to a positioning jig 164. A timing belt 150, which moves loading tool 112 from IC tray 160 to positioning jig 164 has a tension adjuster 152. DC test tool 114, insertion tool 116, and removal tool 118, which are also on frame 10, respectively move IC device 162 to a DC test position 166, insert IC device 162 into and remove IC device 162 from a socket on a burn-in board (not shown). Extension tool 120, which is next to removal tool 118, moves IC device 162 to a turntable 174 that relays burn-in tested IC device 162 to a sorting portion (not shown).
Loading tool 112 and extension tool 120 can easily adapt to a tray type or tube type IC device carrier using a combination of a servomotor and timing belt mechanism and a program modification, without a mechanical replacement. Insertion tool 116 and removal tool 118 operate independently from loading tool 112 and extension tool 120, so as to insert and remove IC device 162 into and from the socket without interfering with loading tool 112 and extension tool 120.
Spline shaft 148 and cylinder 144 of loading tool 112 and the extension tool 120 move IC device 162 in a z-axis direction, and the moving stroke of tools 112 and 120 can be independently adjusted by a program. DC test tool 114, insertion tool 116, and removal tool 118 are tied together by a connection and crank means 154, and move together.
Typically, after the insertion of IC device 162 in the burn-in socket as described above, a contact test checks whether the IC device made a secure contact with the socket. According to the contact test result, an operator corrects any incomplete contacts, and a burn-in board including the IC device in the socket is placed in a burn-in test chamber.
There are a number of causes of incomplete or poor contact between IC devices and sockets. First, a deformation of the IC device pins during handling of the IC devices prior to inserting the devices into the sockets can cause a contact failure between the pins and the socket terminals even when the devices are correctly inserted in the sockets. Second, a deterioration of the socket terminals due to repeated insertion and removal of the IC devices or a defective socket terminal can cause contact problems. Third, a deteriorated or uneven rubber pad, which contacts to the IC device, on the vacuum nozzle may pick up the IC device aslant and thus insert the device into the socket incompletely, causing a contact problem. Fourth, incorrect placement of a burn-in board on a table, which moves the burn-in board, can cause a contact problem. In order to move the burn-in board, two compression cylinders push only one side of the burn-in board. Thus, a slight difference in the pressure or operation timing between the two cylinders can skew the burn-in board slightly on the table. Even though a pick up tool can adapt to a slight misplacement of the burn-in board, factors such as an abrasion of the burn-in board can exacerbate the misplacement, so that the pick up tool cannot adapt successfully. In addition, when a support that supports the bottom side of the burn-in board does not support the burn-in board horizontally, a tilt of the burn-in board can cause an insertion or contact failure of the IC device due to a height difference among the socket terminals.
Optimum handling of IC device handling tools can prevent some contact problems. For example, a slow IC device pick-up by a removal tool can reduce damage on the IC device pins since there is longer time between a beginning of a departure of the IC device from a socket and an end of the departure allows more time for the socket terminals to retract from the IC device pins. When the socket terminals completely retract from the IC device pins, the removal tool picks up the IC device by turning on a vacuum. A correct vacuum-on timing of the removal tool is necessary because a vacuum turn-on prior to a complete retraction can cause an incorrect device pick-up and a damage on the IC device pins. The distance between the vacuum nozzle of the removal tool and the IC device is another factor for a correct IC device pick-up.
When the insertion tool inserts the IC device into the socket, a vacuum of the insertion tool must turn off when the insertion tool is fully extended, and the socket terminals are completely open, so that the IC device correctly falls and sits in the socket. The socket must close slowly so that the socket can correct any slight misplacement of the IC device within the socket without damaging the IC device pins.
The insertion and removal tools move up and down, and right and left. When the tools change their direction of motion, the tools should decelerate slowly enough so as not to shake the IC devices held by the tools. Whereas, when the tools move without having an IC device, the tools can move as fast as the apparatus permits.
Since the table moves with small coordinate deviations, the insertion and removal tools must be able to move slightly in the X and Y directions to adjust to the deviations. A socket guide attached to the tools can achieve the adjustment. An absence of the adjustment may cause a misalignment between the tools and the sockets of the burn-in board.
An exemplary burn-in chamber contains forty-eight burn-in boards, each of which contains one hundred or more IC devices. A typical contact failure ratio before a burn-in test is 5% to 15% for a gull-wing type IC device. Correction of such failures requires an operator to spend 30 minutes to 1 hour. This time spent correcting contact failures can decrease a productivity of a process for manufacturing IC devices.